Abstract: Objective To observe the dynamic changes of immune responses of splenocytes in mice immunized with
recombinant vaccine Bifidobacterium bifidum (pGEX-Sj32) of Schistosoma japonicum and investigate the immunological
mechanism of the vaccine. Methods Eighty-eight BALB/c mice were randomized for immunization with 106 CFU recombinant
vaccine orally or with 105 CFU recombinant vaccine intranasally. Four mice were selected from each group every two weeks to
test the responses of the splenocytes to stimulations with SjAWA or ConA. MTT assay and flow cytometry were used to assess
splenocyte proliferation and the distribution of CD4+ and CD8+ T cells, respectively; the levels of interleukin-10 (IL-10), IL-12
and tumor necrosis factor-α (TNF-α) in the cell culture supernatant were detected by ELISA. Results Regardless of the
stimulations, the splencytes showed significantly enhanced proliferation in weeks 2-16 in oral administration group and in
weeks 2-18 in intranasal group (P<0.01). CD4+ subsets in both two groups increased obviously in weeks 2-12 (P<0.01) but CD8+
subsets remained stable. In oral administration group, the levels of TNF-α, IL-10 and IL-12 increased in weeks 2-14, 2-18 and
2-14, and peaked at week 8, 10 and 6, respectively; in intranasal group, the cytokines increased in weeks 2-14, 2-18 and 2-18,
and peaked at week 8, 10 and 8, respectively. Conclusion The recombinant vaccine rBb (pGEX-Sj32) can induce effective
immune responses in mice.